Supported gas separation membrane and method

ABSTRACT

A method of making a gas separation membrane system by providing a porous support material having deposited thereon a metal membrane layer and imposing upon the surface thereof certain surface characteristics that provide for surface activation that enhances the placement thereon of a subsequent metal membrane layer. The gas separation membrane system is useful in the separation of hydrogen from hydrogen-containing gas streams.

This application is a divisional application of U.S. patent applicationSer. No. 13/071,320, filed on Mar. 24, 2011, which claims priority fromU.S. Provisional Application No. 61/317,894, filed Mar. 26, 2010, theentire disclosure of which is incorporated herein by reference.

The present disclosure relates generally to composite gas separationmodules used to separate a specific gas from a mixture of various gases,and, in particular, to methods of manufacturing and reconditioning suchmodules.

Composite gas separation modules are commonly used to selectivelyseparate specific gases from gas mixtures. These composite gasseparation modules can be made of a variety of materials, but the twomost commonly used materials are polymers and metallic composites. Whilepolymer membranes can provide an effective and cost-efficient option forthe separation of gases at low temperatures, they are often unsuitablefor gas separation processes that require higher temperatures andpressures; because, they tend to thermally decompose. The demand forhigh-temperature processing, along with tighter environmentalregulations, requires composite gas separation modules that provide highflux, high selectivity, and the ability to operate at elevatedtemperatures.

The prior art discloses various types of and methods for making gasseparation membranes that are supported upon porous substrates and thatmay be used in high temperature gas separation applications. Many of theknown techniques for depositing thin, dense, gas-selective membranelayers onto porous substrates use techniques that often leave a surfacethat is not uniform in thickness. One of these techniques is describedin U.S. Pat. No. 7,175,694. This patent discloses a gas separationmodule that comprises a porous metal substrate, an intermediate porousmetal layer, and a dense hydrogen-selective membrane. The patent teachesthat the intermediate porous metal layer may be abraded or polished toremove unfavorable morphologies from its surface, and, thereafter, adense gas-selective metal membrane layer is deposited. Although thepatent suggests that the purpose of the abrading or polishing of theintermediate porous metal layers is to remove unfavorable morphologiesfrom its surface, there is no suggestion that such abrading or polishingmay be used for the purpose of creating a membrane layer with a surfacemorphology so that additional activation is not required. There isfurther no suggestion that the abrading or polishing is to be done so asto impose the intermediate metal layer a certain surface roughness inorder to improve the subsequent deposition of a gas-selective metalmembrane layer.

One method for fabricating a palladium composite gas separation moduleis disclosed in U.S. Patent Publication No. 2009/0120287, which presentsa method of making a metallic composite gas separation membrane system.The membrane system can comprise a porous support, a first membranelayer of a gas-selective material overlying the porous support where asubstantial portion of the membrane layer is removed by the use of anultra-fine abrasive to reduce the membrane thickness, and a second layerof a gas-selective material overlaying the reduced membrane layer. Thefirst membrane layer may comprise palladium that is deposited bymultiple plating cycles. This palladium membrane layer is then abradedto remove a substantial portion of the membrane to reduce its thicknessand polished to a smoother finish. A second palladium layer issubsequently deposited onto the newly reduced layer. The abrading stepprovides for a reduction in the membrane thickness, but there is nomention of it providing for a special surface morphology having enhancedactivation properties for the placement or deposition thereon of anadditional metal membrane layer.

In many of the prior art methods of making metal membranes for use ingas separation that are supported upon a porous substrate, the surfaceof the porous substrate and the surfaces of the metal layers andmembranes between each application thereof are required to be surfaceactivated by contacting them with an activation solution. An example ofsuch an activation solution includes a mixture of stannous chloride(SnCl₂), palladium chloride (PdCl₂), hydrochloric acid (HCl), and water.This method of activation often requires multiple applications of theactivation solution with intervening drying and, even, annealing. Thesewash and dry steps are laborious, they produce hazardous aqueous wastes,and they require a substantial amount of time to complete.

It is, thus, desirable to have a method of making a supported metalmembrane that is thin, dense and relatively uniform in thickness thatmay be used in the separation of gases.

It is further desirable for the method to allow for multiple metalplating steps in the manufacture of a supported metal membrane withoutthe need for intermediate chemical activation of the surfaces of thesupport and of the intermediate metal membrane layers.

It is also desirable for the method to generate reduced amounts of wasteproducts and volatile organic solvents in the manufacturing of asupported metal membrane.

Accordingly, the present invention is directed to a method of making acomposite gas separation module. The method comprises the steps of:providing a porous support having a metal membrane layer; imposing ontothe surface of the metal membrane layer a surface morphology thatprovides for an activated surface having enhanced activation propertiesfor the placement thereon of a subsequent metal membrane layer; placingthe subsequent metal membrane layer upon the activated surface; andannealing the subsequent metal membrane layer to provide an annealedmetal layer.

In another aspect of the present invention, there is a system for makinga composite gas separation module. The system comprises: a poroussupport having a metal membrane layer with a surface; means for imposingonto the surface and the metal membrane layer a surface morphology thatprovides for an activated surface having enhanced activation propertiesfor the placement thereon of a subsequent metal membrane layer; meansfor placing a subsequent metal membrane layer upon the activatedsurface; and means for annealing the subsequent metal membrane layer toprovide an annealed metal layer.

FIG. 1 presents a schematic depiction of a polishing system and a tubethat is being polished of an embodiment of the present invention.

FIG. 2 presents a view of the polishing system and tube along sectionA-A of FIG. 1.

FIG. 3 presents an image obtained from a Nanovea® optical profilometerof one example of the activated surface of the present invention.

FIG. 4 presents a schematic depiction of a first polishing designcreated by a polishing system of the present invention.

FIG. 5 presents a schematic depiction of a second polishing designcreated by a polishing system of the present invention.

FIG. 6 presents a schematic of a third polishing design created by apolishing system of the present invention.

FIG. 7 is a representative profilometer trace taken at one location onthe surface of a tube polished in accordance with the inventive methodand showing certain of the features of the surface morphology of anactivated surface.

The inventive method provides for the production of thin, densegas-selective membranes by the use of multiple metal plating steps butwithout an intermediate treatment with an activation solution of theplated metal surfaces between the plating steps. The elimination of thissurface activation by the use of an activation solution overcomes manyof the problems associated with the prior art surface activationtechniques. For instance, it mitigates some of the problems of slowerand uneven metal plating that are caused by the use of an activationsolution to activate the support and metal layer surfaces in themanufacture of a gas separation module.

The inventive method further provides for a reduction in the overallmanufacturing time of a gas separation membrane module by the use of anactivation technique that does not use a chemical activation solution toactivate the surfaces of the support and plated metal layers of the gasseparation module. Because no activation solution is utilized, there isno need to wash off activation solution between activation steps. Thiselimination of the use of an activation solution can provide anadditional benefit of a more environmentally friendly process due to thereduction of aqueous wastes and volatile organic solvents that aretypically generated by chemical activation methods.

Thus, the inventive method provides for the preparation, orreconditioning, or both, of a gas separation membrane system or acomposite gas separation module. The inventive method may includeplacing a metal membrane layer of a gas-selective metal or material upona porous support so as to provide a porous support and metal membranelayer having a surface which may be activated as described in detailherein so that a subsequent metal membrane layer may more easily beplaced thereon.

The porous support upon which the gas-selective metal membrane layer isdeposited may include any porous metal material that is suitable for useas a support for the gas-selective material and which is permeable byhydrogen. The porous support may be of any shape or geometry; providedthat, it has a surface that permits the layer of gas-selective materialto be applied or deposited thereon. Such shapes can include planar orcurvilinear sheets of the porous metal material having an undersurfaceand a top surface that together define a sheet thickness, or the shapeof the porous substrate can be tubular, such as, for example,rectangular, square and circular tubular shapes that have an insidesurface and an outside surface that together define a wall thickness andwith the inside surface of the tubular shape defining a tubular conduit.In the preferred embodiment, the porous support is cylindrical.

The porous metal material can be selected from any of the materialsknown to those skilled in the art including, but not limited to, (1) thestainless steels, e.g., the 301, 304, 305, 316, 317, and 321 series ofstainless steels, (2) the HASTELLOY® alloys, e.g., HASTELLOY® B-2, C-4,C-22, C-276, G-30, X and others, and (3) the INCONEL® alloys, e.g.,INCONEL® alloy 600, 625, 690, and 718. The porous metal material, thus,can comprise an alloy that is hydrogen permeable and comprises iron andchromium. The porous metal material may further comprise an additionalalloy metal such as nickel, manganese, molybdenum and any combinationthereof.

One particularly desirable alloy suitable for use as the porous metalmaterial can comprise nickel in an amount in the range of upwardly toabout 70 weight percent of the total weight of the alloy and chromium inan amount in the range of from 10 to 30 weight percent of the totalweight of the alloy. Another suitable alloy for use as the porous metalmaterial comprises nickel in the range of from 30 to 70 weight percent,chromium in the range of from 12 to 35 weight percent, and molybdenum inthe range of from 5 to 30 weight percent, with these weight percentsbeing based on the total weight of the alloy. The Inconel alloys arepreferred over other alloys.

The thickness (e.g. wall thickness or sheet thickness as describedabove), porosity, and pore size distribution of the pores of the porousmetal substrate are properties of the porous support selected in orderto provide a gas separation membrane system of the invention that hasthe desired properties and as is required in the manufacture of the gasseparation membrane system of the invention.

It is understood that, as the thickness of the porous support increases,the hydrogen flux will tend to decrease when the porous support is usedin hydrogen separation applications. The operating conditions, such aspressure, temperature, and fluid stream composition, may also impact thehydrogen flux. In any event, it is desirable to use a porous supporthaving a reasonably small thickness so as to provide for a high gas fluxtherethrough. The thickness of the porous substrate for the typicalapplication contemplated hereunder can be in the range of from about 0.1mm to about 25 mm. Preferably, the thickness is in the range of from 1mm to 15 mm. More preferably, the range is from 2 mm to 12.5 mm, andmost preferably, from 3 mm to 10 mm.

The porosity of the porous metal substrate can be in the range of from0.01 to about 1. The term porosity is defined as the proportion ofnon-solid volume to the total volume (i.e., non-solid and solid) of theporous metal substrate material. A more typical porosity is in the rangeof from 0.05 to 0.8, and, even from 0.1 to 0.6.

The pore size distribution of the pores of the porous metal substratecan vary with the median pore diameter typically in the range of fromabout 0.1 micron to about 50 microns. More typically, the median porediameter of the pores of the porous metal substrate material is in therange of from 0.1 micron to 25 microns, and most typically, from 0.1micron to 15 microns.

In the inventive method, there is initially provided a porous supportwhich has been prepared by placing a metal membrane layer of agas-selective metal or material thereon by any suitable means or methodknown to those skilled in the art. Some of the suitable means andmethods of preparing and forming a metal layer upon a support are asdescribed in U.S. Pat. No. 7,175,694 and US Patent Publication2009/0120287, both of which are incorporated herein by reference.Possible suitable means or methods for placing a metal membrane layerupon a support include, for example, the deposition of metal upon asurface by electroless plating, thermal deposition, chemical vapordeposition, electroplating, spray deposition, sputter coating, e-beamevaporation, ion beam evaporation and spray pyrolysis. A preferreddeposition method is electroless plating.

The gas-selective metal or material, as the term is used herein, is amaterial that is selectively permeable to a gas when it is in a form ofa dense (i.e., having a minimum amount of pinholes, cracks, void spaces,etc. that allow the unhindered passage of gas), thin film. Thus, adense, thin layer of the gas-selective material functions to selectivelyallow the passage of the desired gas while preventing passage of othergases. Possible gas-selective metals include palladium, platinum, gold,silver, rhodium, rhenium, ruthenium, iridium, niobium, and alloys of twoor more thereof. In a preferred embodiment of the invention, thegas-selective material is a hydrogen-selective metal such as platinum,palladium, gold, silver and combinations thereof, including alloys. Themore preferred gas-selective material is palladium, silver and alloys ofpalladium and silver. The most preferred gas-selective material ispalladium.

The typical membrane thickness of the gas-selective metal membrane layercan be in the range of from 1 micron to 50 microns. For many gasseparation applications, however, a membrane thickness in the upper endof this range may be too thick to provide for a reasonable gas flux thatallows for the selection of a desired gas. Also, various prior artmanufacturing methods often provide gas separation membrane systemshaving the gas-selective membrane layers that are unacceptably thicksuch that they provide for unacceptable gas separation capability.Generally, a membrane thickness that is greater than 20 microns is toolarge to provide for acceptable separation of hydrogen from a gasstream. Even a membrane thickness greater than 15 microns, or even 10microns, is not desirable.

The inventive method provides a way of activating the surface of aporous support that has a metal membrane layer thereon but without thechemical treatment of its surface by the application of a chemicalactivation solution. The purpose of the activation of the surface is toprovide for the subsequent laydown of one or more metal membrane layersby deposition of or plating with a gas-selective metal. In certain ofthe prior art methods of preparing supported metal membrane systems,when multiple metal membrane layers are placed upon the surface of theporous support, there is typically a need for the surfaces of each metalmembrane layer to be activated between each plating or deposition step.In the instant method, however, no chemical means is used to provide forsurface activation, but, rather, an activated surface is provided byimposing onto the surface of the porous support having the metalmembrane layer a particular surface morphology. This surface morphologyis such that it provides for an activated surface having enhancedactivation properties that allow for the placement upon the activatedsurface of a subsequent metal membrane layer.

The specific surface morphology that is imposed upon the surface of thesupported metal membrane is an important aspect of the inventive method.The prior art indicates that the polishing of the metal surfaces of amembrane between metal deposition or plating steps is important in orderto remove imperfections in the membrane layer and to provide for thin,uniform metal layers of metal membrane material upon which furtherlayers of metal may be deposited. It has been thought that it is best tohave a highly polished and smooth surface of the metal layer in betweenthe platings. But, it has been found that certain physicalcharacteristics, also referred to herein as surface morphology, of thesurface of the metal membrane layer that lies upon a porous support cancontribute to surface activation that enhances the placement ofadditional layers of metal membrane material thereon.

The particular surface morphology that is to be imposed upon the surfaceof the supported metal membrane concerns the roughness or texture of thesurface. Contrary to what was previously believed, it is not asdesirable for the surface to which a metal membrane layer is to beapplied to be finely polished; but, rather, it should have a certaintopology that may be defined by various of the profile roughnessparameters that are often used by those skilled in the art to define theroughness properties of a surface. The surface profile may be measuredor determined by using any of the methods or means known to thoseskilled in the art. One example of equipment means for measuring asurface profile to quantify its roughness is a profilometer. Anycommercially available profilometer may be used, such as the opticalprofilometer, identified as the ST400 Optical Profilometer, that ismarketed and sold by Nanovea®. This unit may be used to measure, analyzeand quantify the surface morphologies and topographies of certain userdefined surfaces.

The roughness parameters that may be used to define the surfacemorphology of the invention include such parameters as the mean surfaceroughness or arithmetical mean height (Sa), root mean square height orRMS surface roughness (Sq), skewness of the height distribution (Ssk),kurtosis of the height distribution (Sku), maximum peak height (Sp),maximum pit height, also referred to as maximum valley depth, (Sv), andmaximum height (Sv). These roughness parameters are well known to thoseskilled in the art of measuring and characterizing the roughness andother features of surfaces. These particular parameters characterize asurface based on its vertical deviations of its roughness profile fromthe mean line.

The surface roughness may also be in the form of a lay pattern, which isa repetitive impression upon the surface of the supported metal membranelayer. Examples of surface finish lay patterns include vertical,horizontal, radial, cross-hatched, circular, sinusoidal, oval,elliptical, coil, peanut shaped and other patterns. Suitable andpreferred lay patterns and some of the methods and means for impressingor imposing such lay patterns upon the surface of a supported metalmembrane are discussed in more detail elsewhere herein.

The surface morphology may be imposed upon the surface of the supportedmetal membrane by any suitable method or means known to those skilled inthe art that will give the desired surface morphology for providing anactivated surface. As will be discussed in more detail elsewhere herein,the method of polishing the surface of the supported metal membrane canhave a significant effect upon its resulting surface roughnesscharacteristics and the particular lay pattern that is impressedthereon.

To provide for the desired surface activation of the supported metalmembrane layer, its surface morphology should be such that it has aroughness characteristic wherein for any selected surface area on theactivated surface it has a mean surface roughness (Sa) in the range offrom 0.05 microns (μm) to 0.8 microns (μm). It is preferred for the meansurface roughness to be in the range of from 0.1 microns (μm) to 0.6microns (μm), and, more preferred, from 0.2 microns (μm) to 0.5 microns(μm).

Another surface roughness characteristic of the surface morphology ofthe supported metal membrane layer is its root mean square roughness,which for any selected surface area on the activated surface, the rootmean square roughness (Sq) can be in the range of from 0.1 microns (μm)to 1 microns (μm). It is preferred for the root mean square roughness tobe in the range of from 0.15 microns (μm) to 0.8 microns (μm), morepreferred, from 0.2 microns (μm) to 0.6 microns (μm), and, mostpreferred from 0.2 μm to 0.4 μm.

The skewness and kurtosis of the height distribution of the surface ofthe supported metal membrane may also be used to characterize thesurface morphology that affects the activation properties of the surfaceof the supported metal membrane layer. The surface skewness (Ssk) canhave a value in the range of from −0.6 to 0, but it is preferred for thesurface skewness to be in the range of from −0.5 to −0.1. It is morepreferred for the surface skewness to be in the range of from −0.4 to−0.2. Concerning the kurtosis (Sku) of the height distribution, it canhave a value in the range of from 0 to 10, but it is preferred for thekurtosis of the height distribution to be in the range of from 1 to 8.More preferred, it is in the range of from 1 to 6.

The surface roughness may further be characterized by the verticaldeviation of the roughness profile from the mean plane. This verticaldeviation may be defined by the maximum peak height (Sp) of theroughness profile, which is the height between the highest peak and themean plane, and by the maximum pit (valley) depth (Sv), which is thedepth between the mean plane and the deepest valley.

The maximum height of the profile (Sz) is the difference between themaximum peak height (Sp) and the maximum pit depth (Sv), i.e., Sz=Sp−Sv.The maximum peak height (Sp) of the activated surface can be in therange of from 0.5 μm to 10 μm, but it is preferred to be in the range offrom 0.75 μm to 7 μm, and, more preferred, from 1 μm to 4 μm. Themaximum pit or valley depth (Sv) of the activated surface can be in therange of from 0.5 μm to 10 μm, but it is preferred to be in the range offrom 1 μm to 8 μm, and, more preferred, from 1.5 μm to 6 μm.

The following table presents in summary form the various surfaceroughness parameters that may be used to characterize the surfacemorphology that is impressed or imposed upon the surface of thesupported metal membrane layer in order to provide for an activatedsurface that enhances the activation properties for placement thereon ofa subsequent metal membrane layer.

TABLE Roughness Parameters for the Activated Surface of the SupportedMetal Membrane Surface Roughness Preferred More Preferred ParameterBroad Range Range Range Mean surface 0.05 to 0.8 μm 0.1 to 0.6 μm 0.2 to0.5 μm roughness (Sa) mean squared 0.1 to 1 μm 0.15 to 0.8 μm 0.2 to 0.6μm surface roughness height (Sq) surface skewness −0.6 to 0 −0.5 to −0.1−0.4 to −0.2 (Ssk) kurtosis (Sku) 0 to 10 1 to 8 1 to 6 maximum peak 0.5to 10 μm 0.75 to 7 μm 1 to 4 μm height (Sp) maximum pit 0.5 to 10 μm 1to 8 μm 1.5 to 6 μm height (Sv)

A preferred lay pattern for imposing upon the surface of the supportedmetal membrane is a cross hatched pattern in the shape of an “X” withthe intersecting lines of the cross hatching being placed at particularangles to each other and at particular scratch depths within thesurface. It is preferred for the intersecting lines of the crosshatching be at an angle to each other in the range of from 10° (170°) to90°, or from 25° (155°) to 90°, or from 30° (150°) to 90°. The scratchdepth of these intersecting lines should be in the range of from 0. 2 μmto 1.5 μm as measure from the outer surface of the metal membrane layer.Preferably, the scratch depth of the intersecting lines is in the rangeof from 0.1 μm to 1 μm, and, most preferred, the scratch depth is in therange of from 0.2 μm to 0.5 μm.

Any suitable means or method known to those skilled in the art forimposing or impressing into, onto or upon a surface a desired roughnessor texture or lay pattern of particular characteristics may be used inthe inventive method. There are a wide variety of polishing and machinetools that may be used as means for imposing onto the surface of asupported metal membrane a particular surface morphology including, forexample, various mechanical planarization machines and computernumerical controlled machines. The abrasion surfaces may be selectedfrom a variety of polishing pads, abrasive belts and other abrasivesurfaces. Examples of abrasives that may suitably be used are disclosedin US Patent Publication 2009/0120287.

Any suitable means or method for placing the subsequent metal membranelayers of gas-selective metal upon the activated surface may be usedincluding those disclosed in U.S. Pat. No. 7,175,694 and US PublicationNo. US 2009/0120287.

After the placement of each subsequent metal membrane layer upon anactivated surface, the subsequent metal membrane layer is annealed. Thisannealing or heat treating may be done in the presence of or under agaseous atmosphere that can include simply air, or hydrogen, or oxygen,or any of the inert gases such as nitrogen, helium, argon, neon, carbondioxide or a combination of any of these. The heat treatment may beconducted under temperature and pressure conditions and for the timeperiods as are disclosed in US Patent Publication No. US 2009/0120293,which is incorporated herein by reference, or even the heat treatmentmethod disclosed in US2009/0120293 may be used in the method describedherein.

The surface activation, the placement of the subsequent metal membranelayer, and the annealing steps may be repeated one or more times toprovide the final composite gas separation module of desired propertiesof the invention.

In one embodiment of the invention, a surface morphology is imposed uponthe surface of a tubular porous support (tube) having on its outersurface a layer of gas-selective metal or material so as to provide foran activated surface. The tube may be placed in any suitable turningmachine means for rotating the tube about a horizontal axis such as alathe. An abrading means such as a linear polishing belt or polishingpad or any other suitable abrading device is pressed against therotating tube. The orientation of the abrading device relative to thetube and the relative rotating tube speed and rotating or movingabrading device speed all may be adjusted in a way so as to provide thedesired surface lay patterns and roughness parameters. The rotationalspeed of the tube typically depends upon the particular equipment used.For instance, buffing machine can operate at rotational speeds of from3000 rpm to 6000 rpm, or lathes can operate at rotational speeds of from30 to 500 rpm. When a lathe is used as the rotating means the preferredrotational speed is between 40 to 250 revolutions per minute (rpm).

Referring now to FIG. 1 in which is presented a side elevation view ofsystem 10 that includes a tubular shaped porous support 12 havingdeposited thereon a metal membrane layer 14. The tubular shaped poroussupport 12 with its metal membrane layer 14 has a surface 16 and atubular wall 18 having a wall thickness. The tubular shaped poroussupport 12 is affixed to a turning device or means such as a lathe (notshown) by holding means 20. Holding means 20 may be any suitable meanssuch as a clamping means using, for example, a chuck or collet, or afaceplace with a clamp or any other suitable means for affixing thetubular shaped porous support 12 to a spinning device such as a spindle.The tubular shaped porous support 12 is rotated about its axis in thedirection as shown by arrows 22 by the turning device or means.

Further shown is abrading device or means 24, which may include a planarabrading belt 26 that is moved linearly by the aid of rollers 28 used tomove the planar abrading belt 26 in the direction shown by arrow 30. Itis understood that the abrading device or means 24 may be any othersuitable type of abrading device and it is not limited to planarabrading belts. The abrading device or means 24 may be selected fromother suitable devices or means such as polishing pads, brushes, buffingwheels, and the like.

To impose upon surface 16 a desired surface morphology that provides foran activated surface having enhanced activation properties for theplacement thereon of an additional metal membrane layer, the planarabrading belt 26 is pressed against the tubular shaped porous support 12and moved in the directions indicated by arrow 32. The force at whichthe planar abrading belt 26 is pressed against the tubular shaped poroussupport 12, the rotational speed at which the tubular shaped poroussupport 12 is rotated about its axis as shown by arrows 22, the speed atwhich planar abrading belt 26 is moved along the direction as shown byarrow 30, and the properties of the abrading surface of the planarabrading belt 26 are all properly adjusted and controlled so as toprovide for the desired surface morphology to activate surface 16.

FIG. 2 presents an elevation view of section A-A of FIG. 1 showingsystem 10 from its side. Holding means 20 is shown with tubular shapedporous support 12 placed on the opposite side of holding means 20.Tubular wall 18 is shown with broken lines. Tubular shaped poroussupport 12 is rotated about its axis in the direction shown by arrow 22.The abrading device or means 24 includes the planar abrading belt 26that is moved in the direction shown by arrow 30 by rollers 28 that arerotating about their axes in the direction shown by arrows 32. Planarabrading belt 26 is pressed against surface 16 and is moved along thelength of tubular shaped support 12. As indicated above, the force atwhich the planar abrading belt 26 is pressed against the tubular shapedporous support 12, the relative movement speeds of the tubular shapedsupport 12, planar abrading belt 26, and the properties of the planarabrading belt 26 are adjusted and controlled so as to impose the desiredsurface morphology upon surface 16.

FIG. 3 is a Nanovea® optical profilometer image of an activated surfacehaving a surface roughness with specific characteristics and propertiesprovide for an activated surface ready for the placement thereon of ametal membrane layer.

Referring to FIGS. 4, 5 and 6, these show the top view of geometricpatterns that can be created by the systems and methods of the presentinvention. For example, FIG. 5 is a top view of system 10 shown creatinga figure eight-shaped polishing pattern 40 on surface 16 of tubularshaped support 12. The pattern is produced as tubular shaped poroussupport 12 is rotated about its axis as shown by arrows 22 and abrasivepad or disk 42 contacts surface 16. Abrasive pad or disk 42 is rotatedabout its axis as shown by arrow 44 and as it is pressed against surface16 it is moved about in the figure eight-shaped polishing pattern 40 tothereby impose upon surface 16 a desired surface morphology foractivating surface 16.

FIG. 5 is a top view of system 10 as depicted in FIG. 4 creatingelliptical polishing pattern 50 on tubular shaped porous support 12.Abrasive pad or disk 42 is rotated about its axis as shown by arrow 44and as it is pressed against surface 16 it is moved about in theelliptical shaped polishing pattern 50 to thereby impose upon surface 16a desired surface morphology for activating surface 16.

FIG. 6 is a top view of system 10 as depicted in FIG. 4 creatingintersecting scratches in circular patterns 60 on tubular shaped poroussupport 12. Abrasive pad or disk 42 is rotated about its axis as shownby arrow 44 and as it is pressed against surface 16 it is moved about inthe intersecting scratches in circular patterns 60 to thereby imposeupon surface 16 a desired surface morphology for activating surface 16.

To illustrate certain of the features of an activated surface of asupported metal membrane, presented in FIG. 7 is a representativeprofilometer trace 70 along a path upon an activated surface of a metalmembrane layer. The vertical depth of surface scratches is shown on they-axis of profilometer trace 70 and the points along the path of theprofilometer trace 70 is shown on the x-axis of profilometer trace 70.

That which is claimed is:
 1. A system for making a composite gasseparation module, wherein said system comprises: a porous supporthaving a metal membrane layer thereon with a surface; means for imposingonto said surface and said metal membrane layer a surface morphologythat provides for an activated surface having enhanced activationproperties for the placement thereon of a subsequent metal membranelayer; means for placing said subsequent metal membrane layer upon saidactivated surface; and means for annealing said subsequent metalmembrane layer to provide an annealed metal layer.
 2. The system asrecited in claim 1, wherein said means for imposing includes a polishingpaper having abrading particles with an average particle diameter in therange of from 1 to 10 microns.
 3. The system as recited in claim 2,wherein said abrading particles of said polishing paper comprise acompound material selected from a group consisting of silicon carbide,alpha alumina, zirconia, ceria, yttria, calcium, magnesium, and acombination thereof.
 4. The system as recited in claim 1, wherein saidmeans for imposing includes an abrasive device rotating in the samedirection as said porous support, wherein said abrasive device movesalong the axis of rotation of said porous support.
 5. The system asrecited in claim 1, wherein said surface morphology comprises aroughness wherein for any selected surface area on said activatedsurface, said any selected surface area has a mean surface roughness inthe range of from 0.2 to 0.5 microns.
 6. The system as recited in claim5, wherein said roughness within said any selected surface area has aroot mean square in the range of from 0.2 to 0.5 microns.
 7. The systemas recited in claim 6, wherein said roughness within said any selectedsurface area has a skewness in the range of from −0.6 to
 0. 8. Thesystem as recited in claim 7, wherein said roughness within said anyselected surface area has a kurtosis in the range of from 0 to
 10. 9.The system as recited in claim 8, wherein said surface morphologycomprises geometric patterns selected from a group consisting ofsinusoidal, coil, oval, circular, elliptical, peanut, and figure eight.10. The system as recited in claim 8, wherein said surface morphologycomprises intersecting lines wherein said intersecting lines intersectat angles in the range of from 10-90 degrees and said intersecting lineshave a depth in the range of from 0.1 to 1.5 microns.